<template>
    <div>
        <router-link tag='div' to='/' class="header-abs" v-show="!showAbs">
            <div class="iconfont header-abs-back">&#xe624;</div>
        </router-link>
        <div :style="styleOpacity" class="header-fixed"  v-show="showAbs">
            <router-link to="/">
              <div class="iconfont header-fixed-back">&#xe624;</div>
            </router-link>
            景点详情
        </div>
    </div>
</template>
<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: false,
      styleOpacity: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      let top = document.documentElement.scrollTop
      if (top > 60) {
        let styleOpacity = top / 140
        styleOpacity = styleOpacity > 1 ? 1 : styleOpacity
        this.styleOpacity.opacity = styleOpacity
        this.showAbs = true
      } else {
        this.showAbs = false
      }
    }
  },
  mounted () {
    window.addEventListener('scroll', this.handleScroll)
  },
  // 页面发生变化时，执行下面函数，不然这种没绑定的函数会全局执行
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>
<style lang="stylus" scoped>
  @import '~style/variable.styl'
  .header-abs
    position: absolute
    left: .2rem
    top: .2rem
    width: .8rem
    height: .8rem
    line-height: .8rem
    border-radius: .4rem
    text-align: center
    background: rgba(0, 0, 0, .8)
    .header-abs-back
      color: #fff
      font-size: .4rem
  .header-fixed
    z-index: 2
    position: fixed
    top: 0
    left: 0
    right: 0
    height: $headerHeight
    line-height: $headerHeight
    text-align: center
    color: #fff
    background: $bgColor
    font-size: .32rem
    .header-fixed-back
      position: absolute
      top: 0
      left: 0
      width: .64rem
      text-align: center
      font-size: .4rem
      color: #fff
</style>
